ISSN:
1432-1912
Keywords:
Anaphylaxis
;
Guinea-pig heart
;
Methacholine
;
Cysteinyl-leukotrienes
;
Thromboxane B2
Source:
Springer Online Journal Archives 1860-2000
Topics:
Medicine
Notes:
Summary The effects of muscarinic receptor stimulation by infusions of methacholine (6.25 × 10−8 mol/min or 1.9 × 10−7 mol/min) into isolated perfused, spontaneously beating sensitized guinea-pig hearts on the anaphylactic release of cysteinyl-leukotrienes (LT) and thromboxane (TX) B2 were investigated. Methacholine increased coronary flow and decreased heart rate under basal conditions. Furthermore, infusions of methacholine (1.9 × 10−7 mol/min) significantly increased the anaphylactic release of TXB2 as well as of immunoreactive cysteinyl-LT, which were demonstrated by reversed phase high pressure liquid chromatography to consist of a mixture of LTC4, LTD4 and LTE4. Infusions of atropine (1.3 × 10−7 mol/min) alone did not significantly affect coronary flow and heart rate prior to ovalbumin injection nor anaphylactic release of cysteinyl-LT. The anaphylactic release of TXB2 was, however, significantly decreased in the presence of atropine. Atropine (1.3 × 10−7 mol/min) infused in addition to methacholine (1.9 × 10−7 mol/min) abolished the effects of the muscarinic receptor agonist on spontaneous heart rate and significantly antagonized the increase in coronary flow prior to ovalbumin injection. Similarly, the simultaneous infusion of atropine abolished the effects of methacholine on the anaphylactic release of TXB2 and cysteinyl-LT. After antigen challenge hearts infused with methacholine, atropine or the combination of both drugs did not exhibit any differences with respect to anaphylactic changes of heart rate or the time course of anaphylactic coronary flow reduction. Thus, in the isolated perfused anaphylactic guinea-pig heart, muscarinic receptor stimulation significantly enhanced the release of the arachidonic acid-derived mediators TXB2 and cysteinyl-LT. This enhanced release of vasoconstrictor eicosanoids was, however, not accompanied by an increased coronary vasoconstriction, probably because of the counter-acting vasodilator effect of methacholine.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00179333
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